public List<List<Integer>> fourSum(int[] nums, int target) {

List<List<Integer>> lists = new ArrayList<>();

Arrays.sort(nums);

for (int i = 0; i < nums.length - 3; i++) {

if (i != 0 && nums[i] == nums[i - 1]) continue;

for (int j = i + 1; j < nums.length - 2; j++) {

if (j != i + 1 && nums[j] == nums[j - 1]) continue;

int l = j + 1, r = nums.length - 1;

while (l < r) {

int sum = nums[i] + nums[j] + nums[l] + nums[r];

if (sum == target) {

lists.add(Arrays.asList(nums[i], nums[j], nums[l], nums[r]));

while (l < r && nums[l] == nums[l + 1]) l++;

while (l < r && nums[r] == nums[r - 1]) r--;

l++;

r--;

} else if (sum < target) {

l++;

} else r--;

}

}

}

return lists;

}

public static void main(String[] args) {

//int[] nums = {-3, -2, -1, 0, 0, 1, 2, 3};

//int[] nums = {0, 0, 0, 0};

int[] nums = {-1, 0, 1, 2, -1, -4};

Sum4 t = new Sum4();

System.out.println(t.fourSum(nums, -1));

}

}